O1M TRANSMISSION REBUILD

A quick question, if an automatic transmission is in need of a rebuild , wouldn't something show up on a scan with the hex tool? Or not? The car is a 2002 vw Cabrio with a 01M automatic transmission?

Not necessarily. A scan tool can only tell you what the car knows. The car (in this case the TCM) is pretty good at detecting electrical problems, but it has almost no means of detecting mechanical problems inside the transmission.

How many miles on the car?

01M transmissions don't have the best reputation for longevity, especially if they aren't maintained with regular fluid changes (which VW in its infinite wisdom claims aren't necessary at all).

-Uwe-